Hereinafter a chip package is referred to as a package including within, for example, an integrated circuit such as a large scale integrated circuit (LSI). As is well known, various kinds of test are applied to a product or prototype for evaluating its performances such as performance depending on temperature. In case of temperature test of an LSI chip package, the LSI chip package is connected to a printed circuit board (PCB) or a print wiring board (PWB) via socket(s) and a heat sink is disposed on the LSI package. A temperature-detecting element such as thermistor(s) for sensing temperature is mounted on the heat sink. When the LSI chip package is energizes for operation, the LSI chip package develops heat. And heat energy of the LSI chip package is conducted to the heat sink. The heat energy is radiated in the air from a fin of the heat sink. Accordingly, in this manner, the temperature of the LSI chip package is lowered.
A fan attached to the heat sink generates an air stream along the fin of the heat sink. The more air volume of the air stream is increased, the more radiation efficiency of the heat energy of the heat ink is improved. As a result, the radiation efficiency of the heat of the heat sink is adjusted by controlling the air volume of the air stream. During conducting a temperature test, the air volume of the air stream is controlled according to output data corresponding to the temperature measured by the thermistor. As a result, the temperature of the LSI chip package is set to a specific temperature or the around the temperature. And then, operation check all over the LSI chip package is executed.
Detecting the temperature of the LSI chip package via the heat sink, the thermistor is mounted on the heat sink as described above. Since heat energy of the LSI chip package is conducted to the heat sink and the heat energy is radiated in the air from the heat sink, the temperature of the heat sink is lowered than the actual temperature of the energized LSI chip package. Accordingly, the thermistor cannot accurately detect the actual temperature of the LSI chip package, which may introduce inaccuracy of the temperature test.    [Patent Document 1] Japanese Laid-open Patent Publications No. 2007-234753    [Patent Document 2] Japanese Laid-open Patent Publications No. 2003-234440